I am talking about Antiques, in particular to Chinese Art. The main claim made by Katawiki is that they have a team of experts who revise all the items being listed. In other words, "buy with confidence" because all items have been approved by our experts.
Watching at some of the listings, that claim sound ridiculous at first glance, due to the many bad attributions. But after looking more accurately, it is much worse than ridiculous.
Look for example at ancient Chinese ceramics, in particular at the pottery figures of the Tang and Ming periods, for example. A great quantity of blatant fakes, most on sale by the British shop Pax Romana, a real shame. Horses statues of size and quality that, if genuine, would be the proudly exhibited in specialized Museums, sold at tons for ridiculous prices.
Of course, many apparently validated by a TL test; pity that they are released by a German Lab which is well known for being not reliable.
In conclusion, it is suggested to be cautious while buying on Catawiki, the same way when buying on eBay.